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Ohio State University Extension


Battle for the Belt: Episode 28

Frogeye leaf spot

Episode 28 of Battle for the Belt is now available:

In Episode 28, we talk with Dr. Anne Dorrance about late-season soybean scouting with a focus on Frogeye Leaf Spot and Phytophthora. Dr. Anne Dorrance celebrated her retirement last month, working for Ohio State for 27 years. She was Ohio State Extension’s State Soybean Pathologist. Dr. Anne Dorrance’s work has had a lasting effect on our farmers and agronomists. Thank you Dr. Dorrance for your hard work and dedication to Ohio soybean farmers!

Figure 1. Frogeye leaf spot on the underside of the soybean leaves at the Northwest Research Station.

Dr. Dorrance found Phytophthora sojae at the Northwest Research Station in the soybeans. Phytophthora thrives in Northwest Ohio, and it has for the last fifty years. However, over time, breeders and pathologists have worked together to create varieties that can withstand Phytophthora. Fifty years ago, Phytophthora would have wiped out an entire field, while in our research trials, it caused death in only a few plants. Phytophthora is a water mold that produces swimming spores. When there is an abundance of moisture (i.e., standing water), the spores can spread to root systems, infect the plant, and cause root and stem rot. The visible symptoms are rotted roots and a chocolate brown canker that moves up the stem. The best way to manage this disease is variety selection. Phytophthora used to be controlled by a single resistance gene, so you will see on the bags RPS (i.e., resistance to Phytophthora sojae) 1A, RPS 1C, and RPS 1K; unfortunately, this pathogen has adapted here in Ohio. Dr. Dorrance conducted a recent pathogen survey and concluded that there is a need to focus on quantitative resistance.

Frogeye was also found at the Northwest Research Station. Frogeye leaf spot is caused by Cercospora sojina, a fungal foliar pathogen. The symptoms of Frogeye are tan circular lesions. The centers of the lesions can vary from gray to tan. However, the signature of Frogeye is looking with a hand lens at the underside of the leaf in the center of the lesion and finding fuzzy gray spores (Figure 1). Frogeye leaf spot in this part of the state was previously unusual. Though Northwest Ohio has had historically harsh winters, Frogeye can overwinter on the leaves and stem, as the winter has become milder. For the past ten years, the Lindsey Lab has scouted for Frogeye Leaf Spot in Ohio, which has been most prevalent in southern Ohio from Clinton County to Preble County, even as far north as Mercer, but for the first time last year encountered Frogeye in Northwest Ohio, specifically, Henry County. An R3 fungicide application resulted in about a five-bushel-per-acre yield increase. Along with selecting the most effective variety, scouting now at these late stages is helpful to identify disease issues within your fields to plan for the upcoming season and evaluate the performance of your varieties. Dr. Anne Dorrance shared her top three soybean disease management tips from her time as the State Soybean Pathologist:

1. Scout in the Fall- scouting in the fall tells you what disease issues you are suffering from and how well your varieties are responding to them.

2. Variety Selection- choosing varieties that have the resistance package that you need for your farm, and what is important for the area of the state that you live in. As breeders develop more resistant varieties or as diseases adapt and resistance is less effective, keep yourself up to date with the recommended genetic package for your area.

3. Seed treatment- This tip is geared toward Northwest Ohio because of poor drainage issues and no-tillage systems. These environments are prone to early-season disease development. Identifying which seed treatment package is necessary to protect your crop from the specific diseases in your field.

Battle For the Belt Location Updates

The Wooster location had a planting date of one corn reach R6. The 100-day hybrid across planting dates and locations, reaches maturity first, however, the black layer is difficult to identify as it is not pronounced. This could be an effect of phenotype. In the soybeans, almost every planting date is at R6, waiting on R7. More time is needed to mature to R7, which is one pod on the plant with the full maturity color. There are a couple of soybean plots that are senescing rapidly, due to continued waterlogging.

Corn at the Western is almost completely at R6. We are gearing up to hand-harvest planting dates one, two, and three to do abnormal ear, disease, and yield component evaluations. As we wind down our ear leaf disease evaluations, planting dates four and five at this location seem to have lower disease severity than older planting dates. All soybeans are in R6 (Figure 3.) except for planting date five. The early planting dates are beginning to senesce and dry down. However, they have not reached R7 yet. There is minimal evidence of late-season diseases at this location.

Harvest in the Northwest has begun for planting dates one and two in corn. Planting date three reached R6 (Figure 2.) Planting dates four and five are at R5 and finished up the disease rating. All soybeans at this location have reached full pod except for planting date five. The soybeans are also beginning to senesce at this location. We do have a while before the soybean harvest will begin.

Figure 2. Planting date three at R6 at the Northwest Research Station.  Figure 3. Planting date one soybean at R6 at the Western Research Station.

Table 1. Planting dates one, two, three, four and five in the trial at all three locations with day of planting, soil, air temperature averages, and Growing Degree Days (GDDS). Information from CFAES Weather System,

Table 1. Planting dates one, two, three, four and five in the trial at all three locations with day of planting, soil, air temperature averages, and Growing Degree Days (GDDS). Information from CFAES Weather System,

Keep following the ‘Battle for the Belt’ this growing season to learn more and get further updates! You can find the full video playlist of Battle for the Belt on the Ohio State Agronomy YouTube channel.

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.